U.S. patent application number 17/533018 was filed with the patent office on 2022-05-19 for multiwavelength lidar design.
This patent application is currently assigned to Innovusion Ireland Limited. The applicant listed for this patent is Innovusion Ireland Limited. Invention is credited to Junwei Bao, Yimin Li, Rui Zhang.
Application Number | 20220155449 17/533018 |
Document ID | / |
Family ID | |
Filed Date | 2022-05-19 |
United States Patent
Application |
20220155449 |
Kind Code |
A1 |
Bao; Junwei ; et
al. |
May 19, 2022 |
MULTIWAVELENGTH LIDAR DESIGN
Abstract
A method for enabling light detection and ranging (LiDAR)
scanning is provided. The method is performed by a system disposed
or included in a vehicle. The method comprises receiving a first
laser signal. The first laser signal has a first wavelength. The
method further includes generating a second laser signal based on
the first laser signal. The second laser signal has a second
wavelength. The method further includes providing a plurality of
third laser signals based on the second laser signal; and
delivering a corresponding third laser signal of the plurality of
third laser signals to a respective LiDAR scanner of the plurality
of LiDAR scanners. Each of the LiDAR scanners are disposed at a
separate location of the vehicle such that each of the LiDAR
scanners is capable of scanning a substantial different spatial
range from another LiDAR scanner. LiDAR systems can use
multi-wavelength to provide other benefits as well.
Inventors: |
Bao; Junwei; (Los Altos,
CA) ; Li; Yimin; (Cupertino, CA) ; Zhang;
Rui; (Palo Alto, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Innovusion Ireland Limited |
Los Altos |
CA |
US |
|
|
Assignee: |
Innovusion Ireland Limited
Los Altos
CA
|
Appl. No.: |
17/533018 |
Filed: |
November 22, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15860598 |
Jan 2, 2018 |
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17533018 |
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62477740 |
Mar 28, 2017 |
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62440818 |
Dec 30, 2016 |
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International
Class: |
G01S 17/87 20060101
G01S017/87; G01S 17/10 20060101 G01S017/10; G01S 7/487 20060101
G01S007/487; G01S 7/4865 20060101 G01S007/4865; G01S 17/42 20060101
G01S017/42; G01S 7/481 20060101 G01S007/481; G01S 7/484 20060101
G01S007/484; G01S 17/26 20060101 G01S017/26; G01S 17/931 20060101
G01S017/931 |
Claims
1-15. (canceled)
16. A method for enabling light detection and ranging (LiDAR)
scanning, comprising: at a centralized laser delivery system
mounted on an object: receiving a laser signal having a first
wavelength; dividing the laser signal to generate a plurality of
signals; modulating at least some of the plurality of signals,
wherein at least two modulated signals have different encodings;
and delivering modulated signals and unmodulated signals, if any,
to a plurality of LiDAR scanners mounted on or in proximity to the
object, wherein each of the plurality of signals is delivered to a
respective LiDAR scanner of the plurality of LiDAR scanners.
17. The method of claim 16, wherein each of the plurality of LiDAR
scanners is disposed at a separate location of the object such that
each of the plurality of LiDAR scanners is operative to scan a
substantially different spatial range from another LiDAR
scanner.
18. The method of claim 16, wherein dividing the laser signal to
generate the plurality of signals comprises: dividing the laser
signal to obtain a plurality of divided laser signals; and
amplifying the divided laser signals to generate the plurality of
signals.
19. The method of claim 16, wherein modulating at least some of the
plurality of signals comprises: modulating at least one of the
plurality of signals using an on-off keying (OOK) encoding; and
modulating at least one of the plurality of signals using a pseudo
random bit serial (PRBS) encoding.
20. The method of claim 16, wherein modulating at least some of the
plurality of signals comprises: modulating at least one of the
plurality of signals using one or more of an amplitude modulation,
a phase modulation, or a polarization modulation.
21. The method of claim 16, further comprising: receiving a laser
signal having a second wavelength from a laser source; and
modifying the laser signal having the second wavelength to generate
the laser signal having the first wavelength, wherein the second
wavelength is outside of a wavelength range detectable by a first
type of LiDAR scanner and is within a wavelength range detectable
by a second type of LiDAR scanner.
22. The method of claim 21, wherein the first wavelength is about
775 nm and the second wavelength is about 1550 nm.
23. The method of claim 21, wherein modifying the laser signal
having the second wavelength to generate the laser signal having
the first wavelength comprises using a temperature controlled
periodical poled lithium niobate crystal.
24. The method of claim 21, wherein the wavelength range detectable
by the second type of LiDAR scanner includes the wavelength range
detectable by a InGaAs- or SiGe-based avalanche photo diode.
25. The method of claim 21, wherein the wavelength range detectable
by the first type of LiDAR scanner includes a wavelength range
detectable by a Silicon-based avalanche photo diode.
26. A system for enabling light detection and ranging (LiDAR)
scanning, comprising: a plurality of light detection and ranging
(LiDAR) scanners, wherein each of the plurality of LiDAR scanners
is disposed at a separate location of a mounting object; a splitter
configured to: receive a laser signal having a first wavelength,
and divide the laser signal to generate a plurality of signals; a
modulator configured to modulate at least some of the plurality of
signals, wherein at least two modulated signals have different
encodings; and a plurality of laser delivery channels, wherein each
of the laser delivery channels is configured to deliver a
respective modulated signal or unmodulated signal, if any, to a
respective LiDAR scanner of the plurality of LiDAR scanners.
27. The system of claim 26, wherein each of the plurality of LiDAR
scanners is operative to scan a substantially different spatial
range from another LiDAR scanner.
28. The system of claim 26, wherein the splitter comprises a
passive device including one or more of a beam splitter cube or a
dichroic mirrored prism.
29. The system of claim 26, wherein the splitter comprises an
active device configured to amplify divided signals.
30. The system of claim 26, wherein the modulator is configured to
modulate at least some of the plurality of signals using one or
more of on-off keying (OOK) encoding or pseudo random bit serial
(PRBS) encoding.
31. The system of claim 26, wherein the modulator is configured to
modulate at least some of the plurality of signals using one or
more of an amplitude modulation, a phase modulation, or a
polarization modulation.
32. The system of claim 26, further comprising a frequency modifier
configured to: receive a laser signal having a second wavelength
from a laser source; and modify the laser signal having the second
wavelength to generate the laser signal having the first
wavelength, wherein the second wavelength is outside of a
wavelength range detectable by a first type of LiDAR scanner and is
within a wavelength range detectable by a second type of LiDAR
scanner.
33. The system of claim 32, wherein the frequency modifier
comprises a temperature controlled periodical poled lithium niobate
crystal.
34. The method of claim 32, wherein the wavelength range detectable
by the second type of LiDAR scanner includes a wavelength range
detectable by a InGaAs- or SiGe-based avalanche photo diode.
35. The method of claim 32, wherein the wavelength range detectable
by the first type of LiDAR scanner includes a wavelength range
detectable by a Silicon-based avalanche photo diode.
36. The system of claim 26, wherein the system is for use with a
vehicle or integrated in the vehicle.
37. The system of claim 26, wherein the mounting object where the
system is disposed in or integrated with comprises at least one of:
a robot; a building to enable security monitoring, wherein the
plurality of LiDAR scanners are disposed at a plurality of
locations of the building; and a road to enable traffic monitoring,
wherein the plurality of LiDAR scanners are disposed at a plurality
of intersections or locations of the road.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application Ser. No. 62/440,818, filed Dec. 30, 2016, entitled
"Frequency Modified Laser For Centralized Laser Delivery System In
3d Lidar Design And Fabrication" and U.S. Provisional Patent
Application Ser. No. 62/477,740, filed Mar. 28, 2017, entitled
"Frequency Modified Laser For Centralized Laser Delivery System In
3d Lidar Design And Fabrication." The content of these applications
is hereby incorporated by reference for all purposes.
FIELD
[0002] This disclosure relates generally to laser scanning and,
more particularly, to the use of multiple wavelength light pulses
in light detection and ranging (LiDAR) systems.
BACKGROUND
[0003] LiDAR systems scan light pulses to create an image or point
cloud of the external environment. Some typical LiDAR systems
include a light source, a pulse steering system, and light
detector. The light source generates light pulses that are directed
by the pulse steering system in particular directions when being
transmitted from the LiDAR system. When a transmitted light pulse
is scattered by an object, some of the scattered light is returned
to the LiDAR system as a returned pulse. The light detector detects
the returned pulse. Using the time it took for the returned pulse
to be detected after the light pulse was transmitted, the LiDAR
system can determine the distance to the object along the path of
the transmitted light pulse. By using many light pulses along
different paths, an image or point cloud of the surrounding
environment is created.
SUMMARY
[0004] Examples of the disclosure are directed to a method for
enabling light detection and ranging (LiDAR) scanning. The method
can be performed by a centralized laser delivery system disposed or
included in a vehicle. The method includes receiving a first laser
beam having a first wavelength. The first wavelength is outside a
wavelength range detectable by a plurality of LiDAR scanners. The
method also includes generating a second laser beam based on the
first laser beam. The second laser beam has a second wavelength.
The second wavelength is within the wavelength range detectable by
the plurality of LiDAR scanners. The method further includes
providing a plurality of third laser beams based on the second
laser beam; and delivering a corresponding third laser beam of the
plurality of third laser beams to a respective LiDAR scanner of the
plurality of LiDAR scanners. Each LiDAR scanner is disposed at a
separate location of the vehicle such that each of the LiDAR
scanners is capable of scanning a substantial different spatial
range from another LiDAR scanner.
[0005] In some embodiments, for LiDAR scanners located in different
locations of the system, the system's configurations on detection
range and refresh rate can be different (e.g., significantly
different). In some examples, the laser system can be configured in
a hybrid manner. Some LiDAR scanners may receive a first laser and
some LiDAR scanners may receive a second laser that is frequency
modified. In this kind of hybrid laser system, for example, a
detector in the LiDAR scanner with the first laser may not respond
to or detect the light associated with the second laser due to
different responsive wavelength range; and similarly, a detector in
the LiDAR scanner with the second laser may not respond to or
detect the light associated with the first laser due to different
responsive wavelength range. In such kind of configurations, the
cross talk among the LiDAR scanners within the single system can be
reduced or minimized.
[0006] Furthermore, in some embodiments, the laser power from the
first laser or the second laser can be shared in a time interleaved
manner in addition to being distributed among each scanner at a
fixed percentage. The duty cycle of each scanner can be determined
according to the dark time of each scanner if it is not in a 360
degree scanning, or according to the different priorities in
different scenarios. In some embodiments, due to the limited core
size of a single-mode fiber, the peak power of a laser can be
limited if the beam quality and/or beam divergence is required to
satisfy a predetermined condition (e.g., design specification)
because of this intrinsic nonlinear effect of fiber. To accommodate
this situation, in some examples, a local power booster can be
added to the system to amplify the laser power at the scanner
location to avoid surpassing the power limit when delivering the
light pulses. While the description below uses vehicle as an
example, the centralized laser delivery system and multiple LiDARs
can be disposed in or integrated with robots, multiple locations of
a building for security monitoring purposes, or intersections or
certain location of roads for traffic monitoring, and so on.
[0007] In another embodiment of the present technology, a light
detection and ranging (LiDAR) system having a light source and a
light detector transmits, using the light source, a first pulse
signal at a first wavelength and a second pulse signal at a second
wavelength different from the first wavelength. The first pulse
signal and the second pulse signal are transmitted concurrently or
consecutively. The light detector detects a first returned pulse
signal corresponding to the first pulse signal or the second pulse
signal. The LiDAR system determines based on the wavelength of the
first returned pulse signal whether the returned pulse signal
corresponds to the first pulse signal or the second pulse signal.
In accordance with determining that the returned pulse signal
corresponds to the first pulse signal, the LiDAR system determines
a first range based on timing of receiving the returned pulse
signal and transmitting the first pulse signal. In accordance with
determining that the returned pulse signal corresponds to the
second pulse signal, the LiDAR system determines a second range
based on timing of receiving the returned pulse signal and
transmitting the second pulse signal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1A illustrates an exemplary centralized laser delivery
system and multiple LiDAR scanners disposed or included in a
vehicle.
[0009] FIG. 1B illustrates a block diagram of an exemplary
centralized laser delivery system that enables multiple LiDAR
scanning according to examples of the disclosure.
[0010] FIG. 2 illustrates an exemplary frequency modifier according
to examples of the disclosure.
[0011] FIG. 3 illustrates an exemplary circulator according to
examples of the disclosure.
[0012] FIG. 4A illustrates a block diagram of another exemplary
centralized laser delivery system according to examples of the
disclosure.
[0013] FIG. 4B illustrates a block diagram of another exemplary
centralized laser delivery system according to examples of the
disclosure.
[0014] FIG. 5 illustrates an exemplary flow chart for a method
performed by a centralized laser delivery system disposed or
included in a vehicle.
[0015] FIG. 6 illustrates an exemplary LiDAR system.
[0016] FIGS. 7-11 depicts various exemplary LiDAR systems using
multi-wavelengths according to some embodiments of the present
technology.
[0017] FIG. 12 depicts an exemplary light source.
[0018] FIG. 13 depicts a fiber gain profile for a range of
wavelengths.
DETAILED DESCRIPTION
[0019] In the following description of examples, reference is made
to the accompanying drawings which form a part hereof, and in which
it is shown by way of illustration specific examples that can be
practiced. It is to be understood that other examples can be used
and structural changes can be made without departing from the scope
of the disclosed examples.
[0020] Currently, a single LiDAR scanner is typically disposed
within or on top of the roof of an autonomous vehicle to detect
objects in the vehicle's neighborhood. The LiDAR scanner rotates to
steer the laser beam to detect objects surrounding the vehicle. The
detection coverage and resolution of a single LiDAR scanner may not
be satisfactory or may not meet the requirement for fully
autonomous driving. For example, a single LiDAR scanner may simply
detect an object located at a certain distance to the vehicle, but
cannot provide further information of the object (e.g., height,
size, etc.) due to the resolution and detection coverage limit.
Thus, it is often desired to have multiple LiDAR scanners.
[0021] Current technologies for implementing multiple LiDAR
scanners on a vehicle may require each LiDAR scanner to have its
own laser source and photodetector. This may result in an expensive
system as the number of LiDAR scanners increases and also may
result in loss of power efficiencies. Thus, there is a need for a
centralized laser delivery system that can provide laser signals to
multiple LiDAR scanners from a single laser source. In optical
transmission, routing or delivering of laser signals can be
performed for laser signals having wavelength of, for example,
about 1550 nm. Laser signals having a wavelength of about 1550 nm
are frequently used in optical telecommunication for long distance
signal transmission and for data modulation. However, detecting the
1550 nm wavelength laser signals requires an expensive InGaAs
avalanche photodetectors (APD). An InGaAs APD may have lower
detection sensitivity and quality than a typical Silicon APD, which
is more frequently used as a detector in the LiDAR scanner. In some
examples, InGaAs APD may have a typical noise equivalent power of
10.sup.-14 W/sqrt(Hz), and an intrinsic avalanche gain of about 10
under nominal operation conditions. Further, arrayed InGaAs
detector may not be readily available. On the other hand, in the
1550 nm wavelength band, pulsed fiber laser or fiber coupled laser
can have good beam quality (e.g., M.sup.2<1.2); and the typical
peak power can be about 2 kW with tunable pulse width from about
1-5 ns. Moreover, the fiber coupled nature of devices operating in
the 1550 nm wavelength band requires minimum or no alignment in an
assembly process, thereby enhancing the reliability and
robustness.
[0022] A LiDAR device typically operates within a wavelength band
of about 600-1000 nm, or more specifically about 760-940 nm. In
this wavelength band, Si-APD and diode lasers are frequently used.
A Si-APD has better detection sensitivity and detection limit than
an InGaAs APD; and is relatively inexpensive. For example, a Si-APD
may have a typical noise equivalent power of about 10.sup.-15
W/sqrt(Hz), and an intrinsic avalanche gain of about 100 under
nominal operation conditions. A Si-APD can also be used to readily
form linear or 2D detector arrays. In some examples, the spectrum
of Si-based detectors can be from 400 nm to 1100 nm. Moreover, a
typical high power pulsed diode laser operating within this
spectrum range can have a wavelength of 905 nm and a maximum peak
power of 75 W with micro stack structure of three or four layers.
The typical laser pulse width is about 5-50 ns. Further, a typical
high power pulsed diode laser that operates within this wavelength
band may have a laser beam quality (e.g., M.sup.2 is about 30) that
is worse than that of a pulsed fiber laser or a fiber coupled
laser, because of its astigmatic nature.
[0023] Thus, there is a need of a centralized laser delivery system
that can use 1550 nm wavelength laser signal provided by a
high-quality fiber-based laser to perform data modulation and
delivering of laser signals to multiple LiDAR scanners, while using
a high-quality Si-APD that operates at a wavelength of about
760-940 nm to obtain high detection sensitivity. Combining the
fiber-based laser with Si-APD can improve 3D LiDAR performance. A
3D LiDAR scanner can detect and analyze an object or environment to
collect data of the object such as distance, shape, dimension,
appearance (e.g., color), or the like. The data collected can be
used to construct a digital three-dimensional models. Moreover,
fiber-based laser source can significantly reduce the alignment
requirement and improve manufacturing efficiency. Further,
combining fiber-based laser with a modified wavelength (e.g.,
halved wavelength) with an arrayed silicon detector also enables
building a flash type LiDAR, which can avoid or minimize mechanical
scanning in a conventional LiDAR design. Further, a centralized
laser delivery system provides a flexible system partition that
allows fragile modules or sub-systems to be disposed within
controlled environment. This reduces overall system requirements.
For example, the laser light source can be mounted within the
vehicle cabin; and laser light steering portion of sensor can be
mounted on the roof, behind the windshield, or embedded in the
bumper.
[0024] FIG. 1A illustrates an exemplary centralized laser delivery
system 101 and multiple LiDAR scanners disposed or included in a
vehicle 100. As shown in FIG. 1, a centralized laser delivery
system 101 and a plurality of LiDAR scanners 110A-F (collectively
as LiDAR scanners 110) are disposed in a vehicle 100. In some
embodiments, centralized laser delivery system 101 can be disposed
at or integrate with vehicle 100 at a predetermined position. The
predetermined position may be at, for example, the center of the
vehicle such that the plurality of LiDAR scanners 110A-F is evenly
distributed around the predetermined position of centralized laser
delivery system 101 to receive laser signals. In some examples,
centralized laser delivery system 101 can also be disposed at a
convenient position such as in the neighborhood of control circuits
of vehicle 100. It is appreciated that centralized laser delivery
system 101 can be disposed in any desired position of vehicle
100.
[0025] In some embodiments, centralized laser delivery system 101
can provide laser signals to one or more of the plurality of LiDAR
scanners 110A-F, depending on the status of vehicle 100. For
example, vehicle 100 may be moving forward and thus may require
detecting objects positioned in front of and on the two sides of
vehicle 100, but may not require detecting objects positioned
behind vehicle 100. Accordingly, centralized laser delivery system
101 can provide laser signals to LiDAR scanners 110A-E, but not
LiDAR scanner 110F, which is configured to detect objects
positioned behind vehicle 100. As another example, vehicle 100 may
be moving backward and may require detecting objects positioned
behind vehicle 100. Accordingly, centralized laser delivery system
101 can provide laser signals to LiDAR scanners 110F.
[0026] In some embodiments, centralized laser delivery system 101
can provide laser signals using one or more channels 112A-F
(collectively as channels 112). Channels 112 can be, for example,
optical fiber channels. Channels 112 can be flexible and can thus
enable routing or delivering laser signals to any LiDAR scanners of
vehicle 100. In some embodiments, channels 112 can include
single-mode fibers and/or multi-mode fibers. Channels 112 can
transmit laser signals having any desired wavelength (e.g., about
1550 nm). A laser signal is a signal that carries information using
a laser beam. A laser signal may include one or more laser pulses,
photons, or beams. A laser signal can be modulated or unmodulated.
A laser signal can also have any wavelength and power.
[0027] FIG. 1B illustrates a block diagram of an exemplary
centralized laser delivery system 101 that enables multiple LiDAR
scanning according to examples of the disclosure. In some
embodiments, centralized laser delivery system 101 includes a
modulator 102, a frequency modifier 104, a splitter 106, and a
plurality of isolators 108A-E. Modulator 102 can receive a laser
signal 132 from a laser source (not shown). In some examples, laser
signal 132 can have a specific wavelength (e.g., 1550 nm) for
reducing or minimizing the loss or absorption of a channel for
transmitting the laser signals. Laser signal 132 can include, for
example, a 1550 nm pulsed laser provided by a pulsed fiber laser or
fiber coupled laser (e.g., a free space bulk laser with fiber
coupled output). Modulator 102 can perform encoding of laser signal
132. For example, modulator 102 can perform on-off keying (OOK)
modulation. The encoding of laser signal 132 can also use a pseudo
random bit serial (PRBS) code to enhance the interference immunity
of a LiDAR scanner. Furthermore, the splitter 106 can be replaced
with a configurable optical add-drop module (OADM), an optical
switch, or an optical directional coupler that can be electrically
controlled.
[0028] In some embodiments, modulator 102 can be an optical
modulator including, for example, an amplitude modulator, a phase
modulators, and/or a polarization modulator. In some examples,
modulator 102 can be an electro-optic modulator including one or
more Pockels cells, and optionally additional optical elements such
polarizers. In some examples, modulator 102 can also be an
acousto-optic modulator or a magneto-optic modulator.
[0029] In some embodiments, as shown in FIG. 1B, modulation can be
performed by modulator 102 for laser signal 132 and therefore a
modulated signal can be provided to all LiDAR scanners. In some
embodiments, as shown in FIG. 3, modulation can be performed on a
laser signal transmitted by each individual channel to a
corresponding LiDAR scanner. As a result, laser signals transmitted
in each individual channel has a different encoding (e.g., using a
different PRBS code), thereby further enhancing the interference
immunity between LiDAR scanners. FIG. 3 is described in more detail
below.
[0030] With reference back to FIG. 1B, frequency modifier 104 can
receive laser signal 134 (a modulated signal) or laser signal 132
(an unmodulated signal); and modify the frequency (or wavelength)
of the received laser signal. For example, laser signal 134 can
have a wavelength of 1550 nm, which is a typical wavelength used
for optical telecommunication. In some examples, frequency modifier
104 can double the frequency (i.e., reduce the wavelength by half)
of laser signal 134. Thus, if laser signal 134 has a wavelength of
about 1550 nm, frequency modifier 104 can generate a laser signal
136 having a wavelength of about 775 nm. In some examples, laser
signal 136 can have a wavelength within the range of about 775-785
nm and have a peak power of about 1.5 kW.
[0031] FIG. 2 illustrates an exemplary frequency modifier 104,
which may include a temperature controlled periodical poled lithium
niobate (PPLN) crystal 202. A PPLN crystal can be used to perform
non-linear wavelength conversion such as frequency doubling,
different frequency generation, sum frequency generation, four wave
mixing, optical parametric oscillation, and/or other non-linear
processes. In some embodiments, changing the temperature of the
PPLN crystal can vary phase matching conditions of input photons,
which alters the periodicity of the poling in the PPLN crystal. For
example, by changing the temperature of the PPLN to a specific
temperature, frequency modifier 104 can generate laser signals
having about 775 nm wavelength based on the input laser signals
having about 1550 nm wavelength. Thus, the frequency of the laser
signals is effectively doubled. As described above, the 775 nm
wavelength laser signals are within the detection range of about
600-1000 nm of a Si-APD, and therefore can be detected by a Si-APD
based LiDAR scanner. In some examples, frequency modification using
PPLN crystal can have a conversion efficiency (e.g., 80-90% at
about 500 W peak power level) that is acceptable or satisfactory
for the purpose of providing laser signals to enable LiDAR
scanning.
[0032] In some embodiments, frequency modifier 104 can be placed in
a temperature controlled environment disposed within vehicle 100.
For example, the PPLN crystal may be contained or isolated in an
oven, the temperature of which can be controlled to a predetermined
temperature or a range of temperatures.
[0033] Referring back to FIG. 1B, splitter 106 receives laser
signal 136 with a modified wavelength (e.g., about 775 nm), and can
generate a plurality of laser signals 138A-E based on laser signal
136. For example, as shown in FIG. 1B, splitter 106 can divide
laser signal 136 to multiple laser signals 138A-E, each of which is
provided to a respective isolator 108A-E. In some embodiments,
splitter 106 can include a passive device such as a beam splitter
(e.g., a beam splitting cube, a dichroic mirrored prism, or any
desired arrangement of mirrors or prisms). Splitter 106 can also
include an active device that provides amplifications or
enhancement of the divided laser signals.
[0034] As shown in FIG. 1B, in some embodiments, centralized laser
delivery system 101 can include one or more isolators 108A-E
(collectively as isolators 108). Each of the isolators 108A-E can
receive a corresponding laser signal 138A-E, and can provide an
output laser signal 142A-E, respectively. As described above, each
of laser signals 138A-E can be a modulated and frequency-modified
signal. In some examples, isolators 108A-E allow transmitting of
laser signals in only one direction. For example, isolator 108A
allows transmitting of laser signal 138A to LiDAR scanner 110A, but
would block any laser signal or light travelling backwards to
splitter 106. Isolator 108A can thus prevent unwanted feedback,
such as scattering or reflecting laser signals or light. In some
examples, isolators 108 can allow return signals to be delivered to
the detectors. Isolators 108 can include one or more of
polarization dependent isolators, polarization independent
isolators, and/or any other type of isolators. For example, a
polarization dependent isolator can include an input polarizer, a
Faraday rotator, and an output polarizer. A polarization
independent isolator can include an input birefringent wedge, a
Faraday rotator, and an output birefringent wedge.
[0035] With reference to FIGS. 1A and 1B, in some embodiments, each
of laser signals 142A-E can be provided to a respective LiDAR
scanner 110A-E for performing laser scanning to detect objects
surrounding vehicle 100. A laser signal 142A-E can be provided
using a respective channel 112A-E. As described above, channels
112A-E can be, for example, optical fiber channels. Channels 112A-E
are flexible and can thus enable routing or delivering laser
signals 142A-E to their respective LiDAR scanners of vehicle 100.
In some examples, channels 112 can have a length in the range of
meters. In some examples, a LiDAR scanner 110 can include scanning
optics (e.g., dual oscillating plane mirrors, a polygon mirror, a
dual axis scanner), photodetectors (e.g., Si-APD, SiMP), receiver
electronics, and/or position and navigation systems. It is
appreciated that any number of isolators 108, LiDAR scanners 110,
and channels 112 can be used in a vehicle 100 to enable scanning of
a desired range of spatial distance/angles for detecting objects
around vehicle 100.
[0036] With reference to FIGS. 1B and 3, in some embodiments, one
or more circulators can be used in conjunction with the centralized
laser delivery system 101. For example, one or more circulators can
be disposed between isolators 108 and LiDAR scanners 110. A
circulator can be a non-reciprocal three- or four-port device
(e.g., a waveguide circulator), in which a laser signal entering
any port is transmitted to the next port in rotation. A port of the
circulator is a point where an external channel or waveguide
connects to the circulator.
[0037] With reference to FIG. 3, a circulator 310 can be used to
build a coaxial transceiver. For example, as shown in FIG. 3,
circulator 310 can receive an input signal 312, which may be laser
signal 142 (shown in FIG. 1B). Circulator 310 can rotate input
signal 312 to the next port and transmit a scanning signal 314 to
detect an object within the detection range of a LiDAR scanner.
After scanning signal 314 encounters the object, a return signal
316 can be collected via free space optics and received at another
port of circulator 310, which then rotates return signal 316 to the
next port to provide a signal 318 to a detector for further
processing. A detector can be a Si-APD or a silicon photo multiply
tube (SiPM) detector. A SiPM detector can have good responsivity
towards shorter wavelength (e.g., a wavelength that is shorter than
typical LiDAR application wavelength of about 905 nm) and be used
to further improve detection sensitivity.
[0038] With reference to FIG. 1B, it is appreciated that various
other optical components, such as combiner, optical amplifier,
and/or high speed amplitude/phase modulator, can also be disposed
within or used in conjunction with centralized laser delivery
system 101 and/or LiDAR scanner 110A.
[0039] For example, under certain circumstances, when extra laser
power is required due to scanning range requirements, a local power
booster can be added to a nearby location of a LiDAR scanner (e.g.,
at or nearby the locations of one or more of scanners 110A-E).
[0040] FIG. 4A illustrates a block diagram of another exemplary
centralized laser delivery system 401 according to examples of the
disclosure. As shown in FIG. 4A, centralized laser delivery system
401 can include a splitter 406, a plurality of modulators 402A-E
(collectively as modulators 402), a plurality of frequency
modifiers 404A-E (collectively as frequency modifiers 404), and a
plurality of isolators 408A-E (collectively as isolators 408).
Splitter 406, modulators 402, and isolators 408 can be similar to
those described above in connection with FIG. 1B and therefore are
not repeatedly described.
[0041] In some embodiments, in centralized laser delivery system
401, splitter 406 can be disposed before modulators 402 and
frequency modifiers 404. For example, splitter 406 can receive
laser signal 432 from a laser source (not shown), which can have
about 1550 nm wavelength. Based on laser signal 432, splitter 406
can generate a plurality of laser signals 434A-E, each of which is
provided to a modulator 402A-E, respectively. By disposing splitter
406 before each of modulators 402A-E, the laser signal provided to
each LiDAR scanner can be individually modulated. For example, each
of laser signals 436A-E generated by respective modulators 402A-E
can have different encoding, and in turn each LiDAR scanner can be
provided with a laser signal with different encoding (e.g., encoded
with a different pseudo random bit serial (PRBS) code).
Individually encoding the laser signal for each LiDAR scanner can
enhance the interference immunity of the LiDAR scanners. For
example, neighboring LiDAR scanners (e.g., LiDAR scanners 110A and
110B shown in FIG. 1A) may have a partially overlapping scanning
range such that undesired return signals may be received by the
neighboring LiDAR scanners. These undesired return signals may
interfere with a neighboring LiDAR scanner. By individually
encoding the laser signal for each LiDAR scanner, the interference
from undesired return signals can be reduced.
[0042] With reference to FIG. 4A, individually modulated laser
signals 436A-E can be provided to a respective frequency modifier
404A-E. Frequency modifier 404A-E can generate laser signals
438A-E, respectively. Laser signals 438A-E can have a wavelength
that is different from the wavelength of laser signals 436A-E. For
example, laser signals 436A-E may have a wavelength of about 1550
nm, and laser signals 438A-E may have a wavelength of about 775 nm.
Laser signals 438A-E can then be provided to isolators 408A-E,
respectively, and in turn, provided to respective LiDAR scanners.
In FIG. 4A, the splitter 406 can be, for example, an OADM, a
switch, or a directional coupler. The frequency modifiers 404A-E
can be kept in place or removed according to system and local
scanner requirements.
[0043] It is appreciated that a centralized laser delivery system
can have various different configurations in addition to the
configurations shown in centralized laser delivery system 101 or
401. For example, FIG. 4B illustrates a block diagram of another
exemplary centralized laser delivery system 451 according to
examples of the disclosure. In FIG. 4B, a single frequency modifier
454 can be disposed before splitter 456 and modulators 452A-E.
Frequency modifier 454 can receive a 1550 nm laser signal provided
by a fiber-based laser source, and generate laser signal 463 having
a wavelength of about 775-785 nm. In this configuration, modulation
can still be performed on each laser signal provided to each
individual LiDAR scanners, while reducing the number of required
frequency modifiers. Furthermore, the splitter 456 can be replaced
with, for example, a configurable OADM, an optical switch, or an
optical directional coupler that can be electrically
controlled.
[0044] FIG. 5 illustrates an exemplary process 500 for enabling
light detection and ranging (LiDAR) scanning according to examples
of the disclosure. At block 502, a first laser signal is received.
In some examples, the first laser signal has a first wavelength
(e.g., about 1550 nm), and the first wavelength is outside a
wavelength range (e.g., 600 nm-1000 nm) detectable by a plurality
of LiDAR scanners.
[0045] At block 504, a second laser signal is generated based on
the first laser signal. In some examples, the second laser signal
has a second wavelength (e.g., about 775 nm), and the second
wavelength is within the wavelength range (e.g., about 600 nm-about
1000 nm) detectable by the plurality of LiDAR scanners. In some
examples, the wavelength range (e.g., about 600 nm-about 1000 nm)
detectable by a plurality of LiDAR scanners includes the wavelength
range detectable by a silicon-based avalanche photo diode. In some
examples, prior to generating the second laser signal, the first
laser signal is modulated.
[0046] At block 506, a plurality of third laser signals can be
provided based on the second laser signal. The third laser signals
may be provided using a splitter. At block 508, a corresponding
third laser signal of the plurality of third laser signals can be
delivered to a respective LiDAR scanner of the plurality of LiDAR
scanners. In some examples, each of LiDAR scanners is disposed at a
separate location of the vehicle such that each of the LiDAR
scanners is capable of scanning a substantial different spatial
range from another LiDAR scanner.
[0047] Therefore, according to the above, some examples of the
disclosure are directed to a method for enabling light detection
and ranging (LiDAR) scanning, the method being performed by a
system disposed or included in a vehicle, comprising: receiving a
first laser signal, the first laser signal having a first
wavelength, wherein the first wavelength is outside a wavelength
range detectable by a plurality of LiDAR scanners; generating a
second laser signal based on the first laser signal, the second
laser signal having a second wavelength, wherein the second
wavelength is within the wavelength range detectable by the
plurality of LiDAR scanners; providing a plurality of third laser
signals based on the second laser signal; and delivering a
corresponding third laser signal of the plurality of third laser
signals to a respective LiDAR scanner of the plurality of LiDAR
scanners, wherein each of LiDAR scanner is disposed at a separate
location of the vehicle such that each of the LiDAR scanners is
capable of scanning a substantial different spatial range from
another LiDAR scanner.
[0048] Some examples of the disclosure are directed to a system for
enabling light detection and ranging, the system being disposed or
included in a vehicle, comprising: a plurality of light detection
and ranging (LiDAR) scanners, wherein each of LiDAR scanner is
disposed at a separate location of the vehicle such that each of
the LiDAR scanners is configured to scan a substantial different
spatial range from another LiDAR scanner; a frequency modifier
configured to receive a first laser signal emitted by a laser
source, the first laser signal having a first wavelength, wherein
the first wavelength is outside a wavelength range detectable by a
plurality of LiDAR scanners; generate a second laser signal based
on the first laser signal, the second laser signal having a second
wavelength, wherein the second wavelength is within the wavelength
range detectable by the plurality of LiDAR scanners; a splitter
optically coupled to the frequency modifier, the splitter being
configured to provide a plurality of third laser signals based on
the second laser signal; and a plurality of laser delivery
channels, wherein each of the laser delivery channels being
configured to deliver a corresponding third laser signal of the
plurality of third laser signals to a respective LiDAR scanner of
the plurality of LiDAR scanners.
[0049] Multi-wavelength light pulses can also be used to provide
other advantages in LiDAR systems. Some LiDAR systems use
time-of-flight of light to determine the distance to objects in the
path of the light. For example, with respect to FIG. 6, LiDAR
system 600 (which includes, for example, a laser delivery system
(e.g., a laser source such as a fiber laser), a beam steering
system (e.g., a system of one or more mirrors), and a light
detector system (e.g., a photon detector with one or more optics)
transmits light pulse 602 along path 604 as determined by the
steering of the LiDAR scanner of system 600. When light pulse 602
reaches object 606, light pulse 608 will be reflected back to
system 600 along path 610. The time from when transmitted light
pulse 602 leaves LiDAR system 600 to when returned pulse 608
arrives back at LiDAR system 600 can be measured (e.g., by a
processor or other electronics within the LiDAR system). This
time-of-flight combined with the knowledge of the speed of light
can be used to determine the distance from LiDAR system 600 to
object 606. Additionally, by directing many light pulses to scan
the external environment and using the transmission angle as well
as the determined distance between the object and LiDAR system, an
image of the surroundings covered within the scanning range (field
of view) can be precisely plotted (e.g., a point cloud can be
created).
[0050] The density of points in the plot is equal to the numbers of
pulses divided by the field of view. The density of points is equal
to the numbers of pulses divided by the field of view. Given that
the field of view is fixed, to increase the density of points, more
frequent the LiDAR system should fire a pulse, in another word,
higher repetition rate laser is needed. However, by sending more
frequent pulses, the furthest distance that the LiDAR system can
detect is limited, because the returned signal from far object is
received after the system fires the next pulse and the returns may
get mixed up. To get enough density of points for relatively far
distances, a LiDAR system transmits laser pulses with a repetition
rate between 500 kHz and 1 MHz. Based on the time it takes for a
pulse to return to the LiDAR system, the farthest distance the
LiDAR system can detect is 300 meters and 150 meters for 500 kHz
and 1 Mhz, respectively. The density of points of a LiDAR system
with 500 kHz repetition rate is half of that with 1 MHz. The
present disclosure introduces a practical method to realize a LiDAR
system with a high density of points and ability to measure the
objects in far distance.
[0051] In FIG. 7, LiDAR system 600 has transmitted light pulse 700
along path 702. Object 704 reflects light pulse 706 along path 708
back to LiDAR system 600. Problems can arise when light pulse 602
and 700 are transmitted too close in time. For example, if light
pulse 700 is transmitted after light pulse 602 before light pulse
608 is received back at LiDAR system 600, it is necessary to
disambiguate whether a returned pulse is from light pulse 602 or
700. Even if light pulse 700 is transmitted after light pulse 602,
light pulse 706 may be received before light pulse 608 if object is
704 is closer than object 606. Accordingly, LIDAR system 600 must
determine what transmitted light pulse is responsible for a
returned pulse before a distance (and, optionally, direction) to an
object is determined.
[0052] In some embodiments of the present technology, the above
problem is solved by using different wavelengths of light. For
example, in FIG. 7, LiDAR system 600 transmits light pulse 602 at a
first wavelength and transmits light pulse 702 at a second
wavelength that is different than the first wavelength. In some
cases, LiDAR system 600 can use the frequency modifier technique
described above to generate multiple wavelengths. In other cases,
LiDAR system 600 can use other techniques (e.g., using multiple
laser sources) to generate different wavelengths for different
pulses. When different wavelengths are used for the transmitted
pulses, LiDAR system 600 can use the wavelength of the received
pulses to determine the corresponding transmitted pulse. Techniques
for determining which transmitted light pulse corresponds to a
returned light pulse based on the wavelength of the returned light
pulse are described below.
[0053] In some cases, light pulse 602 and light pulse 700 have
substantially the same other characteristics except wavelength
(e.g., amplitude, width, etc.) but in some cases, it may be
advantageous for the light pulses to be different in other
respects. For example, in FIG. 8, the two light pulses 602 and 800
have different amplitudes (as well as different wavelengths) so
that the returned pulses 802 and 608 will also have different
amplitudes. This is useful, for example, in applications that
require dynamic range. A high-amplitude and a low-amplitude pulse
are transmitted in a scan location (e.g., when an estimated
distance to an object is not known). A higher amplitude light pulse
will provide for a stronger corresponding returned pulse (which is
more easily detectable by a detector) from an object that is far
away as compared to a returned pulse based on a lower amplitude
light pulse. The opposite is also true. A lower amplitude light
pulse will provide for a more moderate corresponding returned pulse
(which does not saturate a detector) from an object that is closer
as compared to a returned pulse based on a higher amplitude light
pulse. This can ensure that regardless of whether an object is
close or far, a returned pulse will produce a signal that is
detectable by a detector of LiDAR system 600 but does not saturate
the detector. Because the two (or more) light pulses of different
amplitude use different wavelengths, it is straight forward for
LiDAR system 600 to determine which transmitted light pulse
corresponds to which returned pulse.
[0054] Light pulses of different amplitudes and/or wavelengths need
not be alternating or transmitted in the same direction as
described with respect to FIG. 8. Instead, they can be transmitted
in any useful scan patterns. For example, in FIGS. 9A-9B, the
amplitudes of light pulses are chosen based on an anticipated range
to an object. Specifically, in FIG. 9A (which is a side view of
LiDAR system 600), transmitted light pulses 800, 900, and 902 all
have the substantially the same amplitude and are transmitted in
sequence before light pulse 602 is transmitted with a higher
amplitude. Light pulses 800, 900, and 902 can have different or the
same wavelengths (but are generally different than that of light
pulse 602). LiDAR system 600 may then repeat this sequence of light
pulses (e.g., along a new scan direction) or use a different
sequence of light pulses (e.g., based on new anticipated ranges to
objects in a new scan direction). As viewed from the side in FIG.
9A, the light pulses are all transmitted along path 604 and light
pulses 906, 904, 802, and 608 are received along path 610. When
viewed from above, LiDAR system 600 may steer these pulses in
different directions (and they may reflect off of different
objects). In FIG. 9B (which is a top view of LiDAR system 600),
light pulses 602, 800, 900, and 902 are transmitted along paths
604a, 604b, 604c, and 604d, respectively. The high amplitude light
pulse 602 is transmitted along path 604a because it has the longest
distance before hitting object 606. While the pulses are depicted
as being transmitting consecutively in a sequential manner, this
need not be the case. For example, light pulses 602 and 800 may be
transmitted concurrently so that the pulses are overlapping (this
applies to the configuration depicted in FIG. 8 as well).
[0055] The wavelength of a returned pulse may be determined using
various techniques. For example, the detector of the LiDAR system
may provide information regarding the wavelength of the returned
pulse. In FIG. 10, LiDAR system 600 includes a detector system
using two detectors and one or more dichromatic optical elements,
such as a filter or mirror, to determine the wavelength of a
returned pulse. LiDAR system 600 includes transmitter 1002 that
transmits light pulse 1004 and 1006, each having a different
wavelength. These light pulses reflect off of object 1008 to
produce light pulses 1010 and 1012 that travel back to LiDAR system
600. Light pulse 1010 travels through dichromatic element 1014
because dichromatic element 1014 has a high transmissivity for the
wavelength of light pulse 1010. This allows detector 1016 (behind
lens 1017) to detect light pule 1010 and for LiDAR system 600 to
determine the wavelength of the returned pulse. In contrast,
dichromatic element 1014 reflects light pulse 1012 because
dichromatic element 1014 has a high reflectivity for the wavelength
of light pulse 1012. This allows light pulse 1014 to be reflected
to detector 1018 (behind lens 1019) and for LiDAR system 600 to be
able to determine the wavelength of the returned pulse. FIG. 11
depicts an alternative configuration of detectors 1016 and 1018.
Instead of using a dichromatic element, dispersion element 1100
(e.g., a prism or grating) is used to direct light pulses 1010 and
1012 to detectors 1016 and 1018, respectively. In this
configuration both detectors share lens 1102, which may reduce the
overall complexity and cost of the detector system. In some cases,
detectors 1016 and 1018 may be the same detector (e.g., use
different portions of the same detector).
[0056] FIG. 12 depicts exemplary light source 1200 that is a part
of a pulse transmitter (e.g., transmitter 1002 of LiDAR system 600,
see FIGS. 6-11). Light source 1200 uses seed 1202 to generate
initial light pulses of one or more wavelengths (e.g., 1550 nm),
which are provided to wavelength-division multiplexor (WDM) 1204
via fiber 1203. Pump 1206 also provides laser power (of a different
wavelength, such as 980 nm) to WDM 1204 via fiber 1205. The output
of WDM 1204 is provided to pre-amplifiers 1208 (which includes one
or more amplifiers) which provides its output to combiner 1210 via
fiber 1209. Combiner 1210 also takes laser power from pump 1212 via
fiber 1211 and provides pulses to booster amplifier 1214 via fiber
1213, which produces output light pulses on fiber 1215. The output
light pulses can then be steered by a system of one or more
reflective components (e.g., a system of one or more mirrors and/or
other optical components, such as one or more dispersion optics) of
the LiDAR system in order to scan the external environment. Light
source 1200 can produce pulses of different amplitudes based on the
fiber gain profile of the fiber used in the source (e.g., for use
with the techniques described with respect to FIGS. 8-9). For
example, FIG. 13 shows an example profile gain that shows how
pulses with different wavelengths have different characteristics.
Accordingly, the fiber can be chosen so that the responses of the
two pulses of different wavelengths have the desired ratio of
amplitudes.
[0057] Although examples of this disclosure have been fully
described with reference to the accompanying drawings, it is to be
noted that various changes and modifications will become apparent
to those skilled in the art. Such changes and modifications are to
be understood as being included within the scope of examples of
this disclosure as defined by the appended claims. For example,
while the centralized laser delivery system and multiple LiDARs are
discussed in the context of being disposed in a vehicle, they can
also be disposed in any other systems or devices such as robots,
multiple locations of a building for security monitoring purposes,
or intersections or certain location of roads for traffic
monitoring, and so on. For instance, in a building, one or more
LiDAR scanners can be disposed at each desired location (e.g.,
front door, back door, elevator, etc.) of the building to provide
3D LiDAR scanning for security monitoring purposes. A centralized
laser delivery system can be disposed at a central location (e.g.,
control room of the building) to provide laser signals to the
multiple LiDAR scanners. In another example, one or more LiDAR
scanners can be disposed at each intersection of a road to monitor
the traffic conditions, and a centralized laser delivery system can
be disposed at a central location (e.g., traffic control center) to
provide laser signals to the multiple LiDAR scanners.
[0058] Exemplary methods, non-transitory computer-readable storage
media, systems, and electronic devices are set out in the following
items:
[0059] 1. A method for enabling light detection and ranging (LiDAR)
scanning, the method being performed by a system disposed or
included in a mounting object, comprising:
[0060] receiving a first laser signal, the first laser signal
having a first wavelength, wherein the first wavelength is within a
wavelength range detectable by a first plurality of LiDAR scanners
and is outside of a wavelength range detectable by a second
plurality of LiDAR scanners; and
[0061] generating a second laser signal based on the first laser
signal, the second laser signal having a second wavelength, wherein
the second wavelength is outside of a wavelength range detectable
by the first plurality of LiDAR scanners and is within the
wavelength range detectable by the second plurality of LiDAR
scanners;
[0062] 2. The method of item 1, the method further comprising:
[0063] providing a plurality of third laser signals based on the
first laser signal;
[0064] providing a plurality of fourth laser signals based on the
second laser signal; and
[0065] delivering a corresponding third laser signal of the
plurality of third laser signals or a corresponding fourth laser
signal of plurality of fourth laser signals to a respective LiDAR
scanner of the plurality of LiDAR scanners, wherein each of LiDAR
scanner is disposed at a separate location of the vehicle such that
each of the LiDAR scanners is capable of scanning a substantial
different spatial range from another LiDAR scanner.
[0066] 3. The method of item 1 or item 2, wherein the first
wavelength is about 1550 nm and the second wavelength is about 775
nm.
[0067] 4. The method of any one of items 1-3, wherein generating
the second laser signal based on the first laser signal uses a
temperature controlled periodical poled lithium niobate
crystal.
[0068] 5. The method of any one of items 1-4, wherein the
wavelength range detectable by the first plurality of LiDAR
scanners includes the wavelength range detectable by a InGaAs- or
SiGe-based avalanche photo diode.
[0069] 6. The method of any one of items 1-5, wherein the
wavelength range detectable by the second plurality of LiDAR
scanners includes the wavelength range detectable by a
Silicon-based avalanche photo diode.
[0070] 7. The method of item any one of items 1-6, further
comprising:
[0071] prior to generating the second laser signal, modulating the
first laser signal.
[0072] 8. A system for enabling light detection and ranging,
comprising:
[0073] a plurality of light detection and ranging (LiDAR) scanners,
wherein each of the LiDAR scanner is disposed at a separate
location of the mounting object such that each of the LiDAR
scanners is configured to scan a substantial different spatial
range from another LiDAR scanner;
[0074] a frequency modifier configured to: [0075] receive a first
laser signal emitted by a laser source, the first laser signal
having a first wavelength, wherein the first wavelength is within
the wavelength range detectable by a first plurality of LiDAR
scanners and is outside a wavelength range detectable by a second
plurality of LiDAR scanners; [0076] generate a second laser signal
based on the first laser signal, the second laser signal having a
second wavelength, wherein the second wavelength is outside a
wavelength range detectable by the first plurality of LiDAR
scanners and is within the wavelength range detectable by the
second plurality of LiDAR scanners;
[0077] 9. The system of item 8 wherein the frequency modifier
includes:
[0078] a first splitter optically coupled to the frequency
modifier, the first splitter being configured to provide a
plurality of third laser signals based on the first laser signal;
and
[0079] a second splitter optically coupled to the frequency
modifier, the second splitter being configured to provide a
plurality of fourth laser signals based on the second laser signal;
and
[0080] the system further comprising: [0081] a plurality of laser
delivery channels, wherein each of the laser delivery channels
being configured to deliver a corresponding third or fourth laser
signal of the plurality of third or fourth laser signals to a
respective LiDAR scanner of the plurality of LiDAR scanners.
[0082] 10. The system of item 8 or 9, wherein the system is for use
with a vehicle or integrated in the vehicle.
[0083] 11. The system of any one of items 8 to 10, wherein the
mounting object where the system is disposed in or integrated with
includes at least one of:
[0084] a robot;
[0085] a building to enable security monitoring, wherein the
plurality of LiDAR scanners are disposed at a plurality of
locations of the building; or
[0086] a road to enable traffic monitoring, wherein the plurality
of LiDAR scanners are disposed at a plurality of intersections or
locations of the road.
[0087] 12. The system of any one of items 8 to 11, wherein the
system includes a hybrid configuration of a first laser and a
second laser having modified frequency when it is shared by
different LiDAR scanners in the system.
[0088] 13. The system of any one of items 8 to 12, wherein the
laser source is configurable to be shared in a time interleaved
manner.
[0089] 14. The system of any one of items 8 to 13, wherein the
laser source is configurable to be time interleaved based on dark
time of a plurality of individual LiDAR scanners.
[0090] 15. The system of any one of items 8 to 14, wherein the
laser source is configurable to be time interleaved based on
priority of each individual LiDAR scanner due to the external
environment.
[0091] 16. A computer-implemented method, comprising:
in a light detection and ranging (LiDAR) system having a light
source and a light detector:
[0092] transmitting, using the light source, a first pulse signal
at a first wavelength and a second pulse signal at a second
wavelength different from the first wavelength, wherein the first
pulse signal and the second pulse signal are transmitted
concurrently or consecutively;
[0093] detecting, using the light detector, a first returned pulse
signal corresponding to the first pulse signal or the second pulse
signal;
[0094] determining based on the wavelength of the first returned
pulse signal whether the returned pulse signal corresponds to the
first pulse signal or the second pulse signal;
[0095] in accordance with determining that the returned pulse
signal corresponds to the first pulse signal, determining a first
range based on timing of receiving the returned pulse signal and
transmitting the first pulse signal; and
[0096] in accordance with determining that the returned pulse
signal corresponds to the second pulse signal, determining a second
range based on timing of receiving the returned pulse signal and
transmitting the second pulse signal.
[0097] 17. The method of item 16, wherein the first pulse signal
and the second pulse signal are separated by a first time
interval.
[0098] 18. The method of any one of items 16-17, wherein the first
pulse signal has a first amplitude, and the second pulse signal has
a second amplitude different from the first amplitude;
[0099] 19. The method of item 18, wherein the first amplitude is
greater than the second amplitude.
[0100] 20. The method of any one of items 16-19, the light source
further comprising a fiber having a first gain characteristic at
the first wavelength and a second gain characteristics different
from the first gain characteristic at a second wavelength;
[0101] 21. The method of any one of items 16-20, further
comprising:
[0102] transmitting, using the light source, a third pulse signal
at the second wavelength and a fourth pulse signal at the first
wavelength, the third pulse signal separated from the second pulse
signal by a second time interval, and the fourth pulse signal
separated from the first pulse signal by a third time interval
different from the second time interval;
[0103] detecting, using the light detector, a second returned pulse
signal corresponding to the third pulse signal or the fourth pulse
signal;
[0104] determining based on the wavelength of the second returned
pulse signal whether the second returned pulse signal corresponds
to the third pulse signal or the fourth pulse signal;
[0105] in accordance with determining that the returned pulse
signal corresponds to the third pulse signal, determining a third
range based on timing of receiving the third returned pulse signal
and transmitting the third pulse signal; and
[0106] in accordance with determining that the returned pulse
signal corresponds to the fourth pulse signal, determining a fourth
range based on timing of receiving the second returned pulse signal
and transmitting the first pulse signal.
[0107] 22. The method of item 21, wherein the third time interval
is greater than the second time interval.
[0108] 23. The method of any one of items 16-22, wherein the light
source includes a first seed configured to produce a first seed
pulse signal at the first wavelength and a second seed configured
to produce a second pulse signal at the second wavelength.
[0109] 24. The method of any one of items 16-23, wherein the light
detector includes a first detector and a second detector.
[0110] 25. The method of item 24 wherein a dichromatic optic
directs returned pulses of the first wavelength to the first
detector and returned pulses of the second wavelength to the second
detector.
[0111] 26. The method of item 24 wherein a dispersion element
directs returned pulses of the first wavelength to the first
detector and returned pulses of the second wavelength to the second
detector.
[0112] 27. The method of item 26, wherein the first detector and
the second detector share a lens.
[0113] 28. A light detection and ranging (LiDAR) system
comprising:
[0114] a light source;
[0115] a light detector;
[0116] a processor coupled to the light source and light
detector;
[0117] memory encoded with a computer program for detecting ranges
to objects using pulse signals of different wavelengths, the
computer program including instructions executable by the processor
for: [0118] transmitting, using the light source, a first pulse
signal at a first wavelength and a second pulse signal at a second
wavelength different from the first wavelength, wherein the first
pulse signal and the second pulse signal are transmitted
concurrently or consecutively; [0119] detecting, using the light
detector, a first returned pulse signal corresponding to the first
pulse signal or the second pulse signal; [0120] determining based
on the wavelength of the first returned pulse signal whether the
returned pulse signal corresponds to the first pulse signal or the
second pulse signal; [0121] in accordance with determining that the
returned pulse signal corresponds to the first pulse signal,
determining a first range based on timing of receiving the returned
pulse signal and transmitting the first pulse signal; and [0122] in
accordance with determining that the returned pulse signal
corresponds to the second pulse signal, determining a second range
based on timing of receiving the returned pulse signal and
transmitting the second pulse signal.
[0123] 29. The LiDAR system of item 28, wherein the first pulse
signal and the second pulse signal are separated by a first time
interval.
[0124] 30. The LiDAR system of any one of items 28-29, wherein the
first pulse signal has a first amplitude, and the second pulse
signal has a second amplitude different from the first
amplitude;
[0125] 31. The LiDAR system of item 30, wherein the first amplitude
is greater than the second amplitude.
[0126] 32. The LiDAR system of any one of items 28-31, the light
source further comprising a fiber having a first gain
characteristic at the first wavelength and a second gain
characteristics different from the first gain characteristic at a
second wavelength;
[0127] 33. The LiDAR system of any one of items 28-32, the computer
program further including instructions executable by the processor
for:
[0128] transmitting, using the light source, a third pulse signal
at the second wavelength and a fourth pulse signal at the first
wavelength, the third pulse signal separated from the second pulse
signal by a second time interval, and the fourth pulse signal
separated from the first pulse signal by a third time interval
different from the second time interval;
[0129] detecting, using the light detector, a second returned pulse
signal corresponding to the third pulse signal or the fourth pulse
signal;
[0130] determining based on the wavelength of the second returned
pulse signal whether the second returned pulse signal corresponds
to the third pulse signal or the fourth pulse signal;
[0131] in accordance with determining that the returned pulse
signal corresponds to the third pulse signal, determining a third
range based on timing of receiving the third returned pulse signal
and transmitting the third pulse signal; and
[0132] in accordance with determining that the returned pulse
signal corresponds to the fourth pulse signal, determining a fourth
range based on timing of receiving the second returned pulse signal
and transmitting the first pulse signal.
[0133] 34. The LiDAR system of item 33, wherein the third time
interval is greater than the second time interval.
[0134] 35. The LiDAR system of any one of items 28-34, wherein the
light source includes a first seed configured to produce a first
seed pulse signal at the first wavelength and a second seed
configured to produce a second pulse signal at the second
wavelength.
[0135] 36. The LiDAR system of any one of items 28-35, wherein the
light detector includes a first detector and a second detector.
[0136] 37. The LiDAR system of item 36 wherein a dichromatic optic
directs returned pulses of the first wavelength to the first
detector and returned pulses of the second wavelength to the second
detector.
[0137] 38. The LiDAR system of item 36 wherein a dispersion element
directs returned pulses of the first wavelength to the first
detector and returned pulses of the second wavelength to the second
detector.
[0138] 39. The LiDAR system of item 38, wherein the first detector
and the second detector share a lens.
* * * * *